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Fear‐induced bradycardia is abnormal in rats with heart failure (1132.3)
Author(s) -
Koba Satoshi,
Hisatome Ichiro,
Watanabe Tatsuo
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.1132.3
Subject(s) - bradycardia , microinjection , heart rate , medicine , endocrinology , atropine , anesthesia , blood pressure
We examined autonomic responses to fear in conscious rats with heart failure (HF) after myocardial infarction and central neural mechanisms for the responses. Rats exposed to 5‐min white noise sound (90 dB) displayed freezing behavior (an index of fear), renal sympathoexcitation, and bradycardia. The bradycardia was parasympathetically mediated since atropine injected intravenously prevented the response in normal rats (N5). In HF rats (N7, fractional shortening<35%), the fear‐induced bradycardia was significantly (P<0.05) larger than that in normal rats (N9). Of note, in HF rats, arrhythmia appeared in association with the reduction in heart rate seen during fear. Moreover, in normal rats (N7), microinjection into the lateral/ventrolateral periaqueductal gray (l/vlPAG) of muscimol, a GABAA receptor agonist, significantly suppressed the bradycardia response to fear. Lastly, in HF rats (N6), microinjection into the l/vlPAG of Tempol, a superoxide dismutase mimetic, significantly suppressed the bradycardia response to fear. Taken together, these results suggest that fear stimulates the l/vlPAG and parasympathetically causes bradycardia in rats, and that brain oxidative stress in HF leads to dysfunction of the l/vlPAG, thereby exaggerating parasympathetic effects on heart rate and elevating risks for cardiovascular events during fear. Supported by Shimane Pref Grant for regional medicine.